Re: Seeking a KVM benchmark

Paolo Bonzini
2014-11-12T17:56:44Z

> Assuming you're running both of my patches (LOAD_EFER regardless of
> nx, but skip LOAD_EFER of guest == host), then some of the speedup may
> be just less code running. I haven't figured out exactly when
> vmx_save_host_state runs, but my patches avoid a call to
> kvm_set_shared_msr, which is worth a few cycles.

Yes, that's possible. vmx_save_host_state is here:

preempt_disable();

kvm_x86_ops->prepare_guest_switch(vcpu); // <<<<
if (vcpu->fpu_active)
kvm_load_guest_fpu(vcpu);
kvm_load_guest_xcr0(vcpu);

vcpu->mode = IN_GUEST_MODE;

srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);

and it's a fairly hot function.

Paolo